Oil-cracking still



F 1,615,583 Jan 25 192? E. c. HERTHEL OIL CRACKING STILL Filed No'v. 28, '1921 A 5 Sheets-sheet 1 9 1927. 'Javi ""5 E. c. HERTHEL a OIL CRACKING STILL l Filed Nov. 28, '1921 5 sheets-sheet 5 ATTORNEYS Passes aan, es, i927,

UNET

rares ears EUGENE al HERTHEL, or naar CHICAGO, INDIANA, AssiGNoR 'ro sINcLArR Rnr'ixi'- ma COMEANY, or CHICAGO, iLLiNoIs, A CORPORATION or MAINE. .l

OIL-CRACKING STILL.

Application filed November 28, 1921. Serial No. 518.446.

My invention relates more particularly to improvements in oil cracking stills of the eneral character of that shown in Patent o. 1,285,000'fgranted to the Sinclair Refiningr Company on the application ofv E. W.v Isom, November 19, 1918. 'In such stills themaiiibody of oil being cracked is confined in a still drum provided with means for the escape of tlie`vapors^of the cracked oil,L and the body oi oil is heated by circulating it through a battery of pipes or tubes vconnected in multiple located in a suitable 'urnace, the battery of pipes being "connected at top and bottom to the still drinn,- and the bottom connection being provided with a circulatingptimp by meansof which the oil is'withdrawn from the drum and forced to the v)o'ottom of the heating pipes and upwardly therethrough and back to the drum. 'My invention relates more articularly to `the -improvement .in means or heating the oil'.

The cracking of crude petroleum or its products, such as gas oil, is accompanied y a separation of carbon andfi'xed gas, the amount of which a function of the temperature and increases very rapidly as the temperature necessary to etl'ect the de sired cracking is exceeded. In the iis-ual practice of cracking oils as carried out in 'stills of the type referred to it has been found desirable to use av temperature ot' about 700 or 800 degrees Fahrenheit. It is necessary that 'substantially this temperan ture be imparted ,to the oil in the battery of heating tubes in the furnace, and therefore a high temperature of the, heating gases is necessary. For high efficiency, and economy, it is desirable to extract from the produts'of combustion the largest ,possible proportion of the heat contained therein and at the saine time to avoid excessive temperatures in any region of the battery ofheating tubes in order to minimize separation of carbor The latter is particularly undesirable because such carbon is inclined to deposit upon the-highly heated surface at which it is released from the oil forming a coating on the tube Walls which in ameasy une insulates' the surface on which the carbon is deposited from the cooling eti'ect of the circulating oil. This aggravates the tendency ot' the heating" tubes to become Superheatedin this'parlicular regionJandj;` f

to develop hot spots which endanger and" sometimes cause the rupture ot the AWalls. of

thc tubes in the region iii question, or iiccesy sitate the shutting down of the still for the pui'poseol' cleaningithe tubes. l1 or maximum economy and efliciencji' it isy therefore desirable in stills ot' the character to which my invention-relates to distribute'y the heat absorption as equally as possible through the battery oli heating; tubes,` orfat least to avoid 'excessive heating-in any region and provide for effective, heat absorption throughout. It 1s inevitable, however, tghatf the heating-gases be at the-maximum`tcm-,-

sorptive capacity throughout the battery, therefore, considerably thc greater partzofq the heat ot' the rases would be absorbed by;y the tubes of the battery` with 'whichithe heating grasos first come into Contact, With:-v

thc result that such tubes would hesubjected@ to severe overheating while the tubes with which the gases later romeincontact would@A not receive as much heat as desir. ble. y The 1,/ front. tubes, or those nearest the firebox of@` the furnace and lirst contacting' with the heating,r gases are subject to the most extreme conditions and normally absorbed the great-` Y est amount of heat. This necessitates frcs.

quent'i'cncwal'ot' these tubes.

Itis oneobjeet of my invention toprof, ,i

vide a heater ot the. character described'in which the disparity in heating etl'ect 'be-i; tween the various' tubes in the battery', and particularly the front tubes first exposed ton,y

the heating gases and,y the remainder of 'the 95 heating surfaces ofV the still, is reduced. to.;

the greatest extent possible, iii which they, tubes more cxposeilf--`fo severe teinperatiire's` 1 and requiring 'renewal may be more readil removed and replaced, and further. in Whic iij the latter tubes may be readily obserijed and their condition noted so that the still mayv be shutfdown before the danger v'point reached.

ing a part of this application I have shown and in they tollowing specification described a preferred form of the invention, lt is to be understood, however, that the specic disclosure is for the purpose of' exemplification only and that the scope of the inven tion is defined in the following claims in which I have endeavored to distinguish.

same; and Fig. 6 diagrariimatically represents in elevation and partly in section the invention as applied to a still of the type to which particular' reference. has been made.

.In the drawings the heater in which my invention is embodied comprises a furnace having a firebox 1an uptake liuc 2, a downtake flue 3 and a stack iiue 4, 4lues 2 and 3 being connected at the tops thereof andthe stack flue connected lto heating flue 3 at the bottom of the latter so that the flow of feo heating gases in the heating iue 3 is generally downward. The battery of heating tubes 5 extendsvertically through the hcating rflue 3, the tubes at' their upper-ends being connected-'to a suitable header 6 whicl'a is connected to an outlet pipe 7 and .supM ported on I-bearns 8 and '9 on top of the furnace. The outlet ipe 7 discharges into lthe still drum 30. 'lllie opening 10 in the top of the furnace through which the tubes extend is sealed by a' cover' of refractory material 1,1. The bottom of thel .heating flue is closed by a baffle' of refractory .mate rial 12 supported on the tubes and by plates 13 resting on said material and on angle bars i4 irl-the furnace wall. ends and beneaththe floor or bottomof the flue the. tubes of the battery are connected to a header 15 to which oil is forced through a pipe :16 connected through a circulating pump 31 to the stilldrum referred to above. A pipe 32 connects the suction side of the pump 3l with the drum. Baiile plates 17 and 18 give the heating gases from the firebox a sinuous course between and around the tubes of the bttery -in their descent through the heating flue to the stack flue.`

It will be observed that, as the oil Hows upwardly through. the. heating tubes and as the furnace gases flow in a generally downward direc-tion about the tubes and first corne in contact withthe upper ends of the tubes, themaximum effect of theheating gases is felt in the upper pass through the tubes where the oil is brought to the highest vtrated in Figs. 3 to 5 of the drawings.

At their lower retenes of tubes 19 near their upper ends, and these' tubes therefore are subjected to the highest temperature and the most severe conditions,

and, other things being equal, would absorb the' greatest amount of heu-t therefrom, the temperature of the gases being constantly reduced as they circulate toward the back ofthe furnace and still further as they circulate through the lower passes between the batiles li and 18 and below the latter. ln order to relatively increase. the heat absor tion of the tubes in the rows other than t e first and thus more' evenly distribute the heat absor' tion betweenthe front row of tubes in t e top pass ,p and the remaining heating surfaces, l greatly'increase the heat transfer areas of the, tubesother than those exposed in the front rotiI of thetop pass.

Accordingy to my invention, this is accom plished by the means more specifically ilsmeans consistsl of bands or rings of castiron or other metal of large superficial area which are'preferablyapplicd throughout so much of the length of said tubes (other than those of the front row) as are exposed to the hotfurnece gases, and are preferably formed in two semi-cylindrical sections 20-21. 'lheV inner bore of the sectional ring is substantially cylindrical and of a size to fit closely the pipe of the still to which it is applied, and the outer .surface of the ring is deeply corrugated or provided with circumferential ribs andinterrnediate recesses, thus providing a very largely increased area in contact with the hot gases. 'lhe ring sections are tightly clamped'together about the pipe to which they are applied by compression bands-23 which may correspond in number to the corrugations ,in the ring, or a less number may be used.

ln the specili,l form of ring shown there are three compression bands applied thereto. As best shown in Figs. fl and #t the compression bands are composed of two members, one 23" of which enciroles threcuuarters of the circumference ol' the ring, and the other of which 23 fills` out the remaining quarter of the circumference, the two sections being drawn tightly together by .screwsl cxtending through lugs 25--25 ou the shorter section and passing to lugs 26-26 on the longer ring section.

According to my invention, all the tubes except those of the front row are covered bythcse hands, but the front row of tubes is left bare whereby the greater heat absorption of the front tubes dus to the high temloo jiu

-the length of the 'front tubes in the top pass ot' the heating flue. but by leaving the tubes of the frontl rou' bare or without rings theyI may readily be removedand replaced, vthe headers` beingctornied withy hand-holes 27 opposite the respective holes 28 which receive the tubes, to ,facilitate such removal and replacement and also the cleaning ot `the tiibes'in position. Normally the holes 27 are closed by plugs Q9. To remove the tubes not' other than Ythe front row requires considerably more time as the heat-conducting rings'ivill [not Apass through the openings in the headers but have to be first removed treni the pipes, llhis is not a matter' of so much ronseqiience, lioii'eier, in respect to these tubes as there is very infrequently need for replacement.

l claim:

.'1. VIn tubular oil cracking stills, a heating flue, a tire-box connected to one end oftheheatiiig tine and a s tack flue connected to the other end thereof, a battery of oil yheatingr tubes connected in multiple arranged in and extending. through the heating flue whereby lie-utili,"r gases i'iasisiinf.,T 'troni the lirebox to the stack tlue pass tliereover in the lieatiiipi tlue, means for circulating oil through the oil lieatin; lf tubes iii a direction generally count-creiii'reiit to the iloiv of heating gases ther-cover, and means arranged Von the oil heating tubes in the said y,heating tlue except those nearest the tire-box for increasing;r theexteinal surface thereof. the oil heat ini: tubes in the said heating' tluc nearest.

thev tire-box having the minimum external arca -exposed to lieatiiifir gases passing through the heating tlue. f

2. ln tubular oil cracking stills, a heatingr tliie.` a tire-box connected to one end ot' the heating flue and a stack Hue connected to the other end thereof, a battery ot oil heating tubes connected in multiple arranged in and extending through the heating flue whereby heating gases passing from the tirebox to the stack flue pass thereover in the heating tiue, and means for circulating oil through the oil heating tubes in multiple in a direction generally countercurrent t0 the flow of heating gases thereover, the oil heating tubes in thesaid heating flue near'- est the tire-box having plain cylindrical eX- ternal surfaces and the remaining oil heat' ing tubes in the said heating ue havingv corrugated external surfaces, whereby. the

oil heatingi tubes in the said heatingr flue which are nearest the lire-box have the least heat absorptive capacity.

In tubular oil cracking; stills, a heating t flue, a tire-box connected to one end of the heating flue and a stack flue 'connected to the other end thereof, and a battery of oil heating vtubes connected in multiple arranged in andextending;` through the lieat-.

ine Hue whereby heating ,eases ,passing from the lire-box to the stack flue pass the-reoverl iii the heating iue, the oil heating tubes, first exposed to heating; gases from the firebox in the said heating tlu'e having a minimum of external surface exposed therein and the remaining oil heating tubes in the said heating flue having: means thereon for ilicreasing the external surface thereof exposed to heatingr gases passingi through the heatingr flue. Y. 4. In an oil cracking still, a furnace having,r a heating flue connected atene end toa fire-box' and at the other end lto`a stack flue, a battery of heatingitubes connected in multiple arranged in and extending through the heating flue in' the furnace, a still drum and connections includingr a pump .for circulatingii oil ltherefrom through the heating' tubes ofthe batte y in multiple and back to the still drum,'batlles' in the heating flue for causing heatingr gases from the' tire-bor thereof. r' v EUGENE C HERTHEL1- 

